The present invention relates to the sterilization and disinfection arts. It finds particular application in conjunction with the assessment of vaporized hydrogen peroxide sterilization systems, and will be described with particular reference thereto. It should be appreciated, however, that the invention is also applicable to other sterilization, disinfection, and sanitization methods.
The reusability of medical instruments has become increasingly important in an effort to provide cost effective health care. Many of the instruments that are now sterilized, such as endoscopes, contain tortuous paths, narrow lumens, and other difficult to sterilize areas. In addition, it is often preferable to sterilize medical instruments in the wrappings used to maintain the sterility of the instruments between sterilization and reuse. Such wrappings increase the difficulty of ensuring successful sterilization of the instrument.
A number of methods have been developed for assessment of sterilization processes that are employed to destroy microorganisms which were deposited on the instruments during use. Biological indicators and chemical indicators are among the techniques currently used for monitoring the effectiveness of sterilization cycles. Biological indicators contain a calibrated population of living organisms, e.g. bacterial spores, having a high resistance to the sterilization process under investigation. After exposure to the sterilization cycle, the indicator is incubated in a bacteriological nutrient media to encourage outgrowth of any remaining viable spores. Growth of microorganisms is an indication that the sterilization process has not been effective. Typically several days to a week are required for a detectable outgrowth.
Chemical indicators contain a substance that exhibits a change in a measurable property under predesignated conditions which are normally coincident with sterilization. Chemical indicators provide an instant readout, but the readout only indicates that the conditions for sterilization were met, without assuring that sterilization in fact occurred. Typically, a biological and/or chemical indicator is placed in the sterilizer, along with the instruments to be sterilized, to assess the effectiveness of the cycle.
A variety of sterilants are now available for sterilization of medical instruments. Hydrogen peroxide vapor is a particularly useful sterilant because of its effectiveness at low temperatures, which avoids degradation of heat-sensitive medical instruments. Hydrogen peroxide decomposes to water and oxygen which are not harmful to medical personnel supervising the sterilization process or to patients. Moreover, the water and oxygen by-products are environmentally safe and require no special processing for disposal.
As for other sterilants, however, medical instruments and their wrappings can provide challenges to the effectiveness of sterilization. Hydrogen peroxide vapor is normally mixed with water vapor which, at the temperatures employed for hydrogen peroxide sterilization, is not a sterilant. Moreover, water vapor permeates into wrappings and narrow lumens more readily than hydrogen peroxide vapor, reducing the effectiveness of the hydrogen peroxide sterilant. In addition, condensed water vapor shields any submerged organisms from the hydrogen peroxide. As a result, complete sterilization of the instrument may not always be effectuated. For this reason, conventional biological and chemical indicators can sometimes over-estimate the effectiveness of hydrogen peroxide sterilization processes for those medical instruments and their wrappings which encourage condensation.
The present invention provides a new and improved hydrogen peroxide sterilization evaluation system which overcomes the above referenced problems and others.